Acetoclastic and hydrogenotrophic methane production and methanogenic populations in an acidic West‐Siberian peat bog

Abstract

Sites in the West Siberian peat bog 'Bakchar' were acidic (pH 4.2-4.8), low in nutrients, and emitted CH4 at rates of 0.2-1.5 mmol m(-2) h(-1). The vertical profile of delta13CH4 and delta13CO2 dissolved in the porewater indicated increasing isotope fractionation and thus increasing contribution of H2/CO2-dependent methanogenesis with depth. The anaerobic microbial community at 30-50 cm below the water table produced CH4 with optimum activity at 20-25 degrees C and pH 5.0-5.5 respectively. Inhibition of methanogenesis with 2-bromo-ethane sulphonate showed that acetate, phenyl acetate, phenyl propionate and caproate were important intermediates in the degradation pathway of organic matter to CH4. Further degradation of these intermediates indicated that 62-72% of the CH4 was ultimately derived from acetate, the remainder from H2/CO2. Turnover times of [2-14C]acetate were on the order of 2 days (15, 25 degrees C) and accounted for 60-65% of total CH4 production. Conversion of 14CO2 to 14CH4 accounted for 35-43% of total CH4 production. These results showed that acetoclastic and hydrogenotrophic methanogenesis operated closely at a ratio of approximately 2 : 1 irrespective of the incubation temperature (4, 15 and 25 degrees C). The composition of the archaeal community was determined in the peat samples by terminal restriction fragment length polymorphism (T-RFLP) analysis and sequencing of amplified SSU rRNA gene fragments, and showed that members of Methanomicrobiaceae, Methanosarcinaceae and Rice cluster II (RC-II) were present. Other, presumably non-methanogenic archaeal clusters (group III, RC-IV, RC-V, RC-VI) were also detected. Fluorescent in situ hybridization (FISH) showed that the number of Bacteria decreased (from 24 x 10(7) to 4 x 10(7) cells per gram peat) with depth (from 5 to 55 cm below the water table), whereas the numbers of Archaea slightly increased (from 1 x 10(7) to 2 x 10(7) cells per gram peat). Methanosarcina spp. accounted for about half of the archaeal cells. Our results show that both hydrogenotrophic and acetoclastic methanogenesis are an integral part of the CH4-producing pathway in acidic peat and were represented by appropriate methanogenic populations.

Discovery of a novel methanogen prevalent in thawing permafrost

“…stordalenmirensis' SSU rRNA gene are present in the non-redundant nucleotide database from 33 locations across four continents (Fig. 3) comprising up to 75% of detected archaeal sequences in some instances 17 . These locations include temperate, subtropical and marine habitats spanning a wide range of physicochemical conditions (Supplementary Tables 8 and 9).…”

Occurrence and distribution of tetraether membrane lipids in soils: Implications for the use of the TEX86 proxy and the BIT index

“…This difference between soils and peat bogs might be the result of a much lower contribution of methanogenic Euryarchaeota, which can contain GDGT I in high amounts (Koga et al, 1993), to the total microbial community in soils. In contrast to peat bogs, where methanogens (Euryarchaeota) can comprise up to 36% of the total microbial community (Kotsyurbenko et al, 2004), little data are available on the abundance of Euryarchaeota in soils. Molecular ecological studies of soils have mainly revealed sequences belonging to the non-thermophilic Crenarchaeota and have rarely revealed clones belonging to the Euryarchaeota (e.g.…”

“…DeLong et al, 1994;MacGregor et al, 1997;Schleper et al, 1997;Vetriani et al, 1999;Jurgens et al, 2000;Karner et al, 2001;Keough et al, 2003), peat bogs, wetlands and soils (e.g. Buckley et al, 1998;Ochsenreiter et al, 2003;Sizova et al, 2003;Kotsyurbenko et al, 2004) and the deep subsurface (Takai et al, 2001). Despite being ubiquitous, only a limited number of archaeal cultures is available, mostly thermophiles and methanogens, one 'symbiont culture' of a mesophilic Crenarchaeota: Cenarchaeum symbiosum, an archaeon living in symbiosis with the marine sponge Axinella mexicana (Preston et al, 1996) and a nitrifying crenarchaeote isolated from a sea aquarium (Kö nneke et al, 2005).…”

Stratified Communities of Methanogens in the Jiulong River Estuarine Sediments, Southern China

“…On the contrary, acetoclastic methanogenensis contributed approximately 70 % of total methane production in freshwater environments because of low sulfate concentration [21,22]. In this study, the fragments affiliated with Methanosaeta and Methanomicrobiales accounted for 21 and 27 % of all fragments averagely.…”